1. Reproductive hormones

2. What is a hormone?

3. Definition of hormone Hormone Greek “I excite” or “I arouse”
First used by Starling in 1895
Classical definition
Chemical signals that travel via bloodstream to affect the function of the distant organ
Regulatory factor
Secretory organ
Target organ/tissue

4. Definition of hormone Hormones Contemporary definition Much broader
Local factors (produced and used without being carried in the bloodstream)
Autocrine (produced and used by the same cell/tissue)
Paracrine (produced by the neighboring cells and transported via the interstitial fluid)

5. GnRH
Hypothalamus
FSH LH
Estradiol
Pituitary
gland
Ovary

6. Granulosa cells
Basement
membrane
Antrum
Oocyte
Theca externa
Theca interna

7. Granulosa
cells (GC)
Theca
cells (TC)
Basement membrane

8. Classes of hormones Three general classes Lipids
Cholesterol derivatives (steroids)
12-C fatty acid derivatives (eicosanoids)
Proteins and polypeptides
Monoamines

9. Cholesterol and its derivatives
Large molecule
Hydrocarbon ring
Highly hydrophobic
Source
Diet
De Novo synthesis
Found in cell membrane

10. Cholesterol and its derivatives
Vitamin D
Bile acid
Lipid digestion
Steroid hormones
Sex steroids
Adrenal steroild
All cholesterol derivatives contain sterol ring

11. Steroid hormones Commonly called sex steroid hormones
Produced mainly by the gonads
Ovaries and testis
Some production by placenta, adrenal gland, and brain
Water-insoluble but lipid soluble
Easily move across the plasma membrane
Bound to Steroid hormone-binging globulin during transport

12. Three classes of sex steroid hormones
Progestin/progestagens
Estrogens
Androgens
Produced through metabolic process
Steroidogenesis

14. Steroidogenesis Source of cholesterol Common pathway Acetate
De Novo Synthesis
Lipoproteins
HDL (humans and rodents)
LDL (cattle)
Common pathway
Conversion of cholesterol to pregnenolone

15. Splits into two different pathway with the same outcome
Delta-4 pathway
Conversion of pregnenolone to progesterone
Conversion of progesterone to androstenedione
Delta-5 pathway
Conversion of pregnenolone to androstenedione

16. Production of estrogens
Final destination of steroidogenesis in the ovary
Conversion of androgens (testosterone) to estradiol-17 beta
Some species (i.e. rats) use delta-4 pathway, whereas others (i.e. cows) prefer delta-5 pathway

17. General function of steroid hormones
Development of physical characteristics
Male and female sex characteristics
Primary (reproductive organs)
Secondary (physical)
Reproductive success
Sexual behavior and libido
Fertility
Pregnancy

18. Eicosanoids Derivative of 12-C fatty acid (Arachidonic acid)
Prostaglandins (more important for reproduction)
Leukotriens
Arachidonic acid released from phospholipid component of the cell membrane
Phospolipase A
Phospholipase C

20. Prostaglandins Produced from leukotriens through cyclooxygenases
No specific organ of production
Originally isolated from prostate gland
Many reproductive organs produce prostaglandins
Quickly metabolized
Lungs

21. Protein hormones Three subclasses Glycoproteins Proteins
Growth hormone
Prolactin
Placental lactogens
Cytokines (immune system)
Polypeptdes

22. Glycoproteins Produced by the anterior pituitary Produced by placenta
Gonadotropins
Follicle-stimulating hormone (FSH)
Luteininzing hormone (LH)
Thyroid-stimulating hormone (TSH)
Less important for regulation of gonadal function
Produced by placenta
Chorionic gonadotropins (CG)
Human (hCG)
Horse (eCG/PMSG)

23. Structural similarity
Two subunits
Alpha
Universal
Beta
Unique to each hormone
Linked together non-covalently (disulfide bridges)
Glycosylated
Attachment of carbohydrate moiety onto the subunits
Unique among hormones

24. Proteins Pituitary hormones Placental hormones
Growth hormone (GH)
Prolactin (PRL)
Placental hormones
Unique to humans, rodents, and ruminants
Placental lactogen (PL)
GH-Variant (GH-V)
Affect metabolism and lactation
Affect ovarian functions

25. Cytokines Different from hormones No specific organ/cells produce
Immune response
Inflammation
Multiple targets
Interactions to modulate activities of other cytokines
Redundant functions
Auto/paracrine factor rather than endocrine factor

26. Ovarian proteins Inhibins Activins
Mullerian inhibitory substance/hormone (MIS)
Two subunits (alpha and beta)
Different combination determines the nature of proteins

28. Polypeptides Small proteins Short in length compared to proteins
Produced by cleaving large preprohormone peptides

29. Hypothalamic neuropeptides
Gonadotropin-releasing hormone (GnRH)
Regulates secretion of LH and FSH
Composed of 10 amino acids

30. Posterior pituitary hormones
Oxytocin
Composed of 9 amino acids
Produced by the neurons within the hypothalamus but secreted by the posterior pituitary gland
Induces contraction of smooth muscles
Critical for milk let-down